Brief Walkthrough by Subleme
Half-Life on SuperCheats.com
Half Life Walkthrough

This is just a quick walkthrough and is not for the entire game.

Intro 

Black Mesa Research Facility 
Black Mesa, New Mexico 
Load the game with "hl.exe -nointro" to skip the long, but cool, intro. 

Anomalous Materials 

1) Follow the green stripe to the locker room, then go left to the HEV room. Press the button on the computer console to open the storage door for the suit.  Walk up to the suit in the chamber that just opened and you'll don the suit automatically.   

Amusement:  Press the button on the main lobby guard's desk
to watch everyone freak out.

2) Follow the blue stripe to the security door, the guard will only open the door for you if you're wearing your HEV suit.  Once inside, it's a straight walk down a few halls and up an elevator or two.  Use the buttons on the elevators to make them work.

3) Once inside the test lab, you'll have to listen to the two scientists talk for a bit, then they will open the door for you.

4) Inside the test chamber, climb to the platform, wait for the switch on the console to open, and then press the switch.

5) Climb back down and walk over to the cage.  When it opens, get behind
the cart and push it into the particle beam.  Then pay attention, this is a cool part.

Unforeseen Consequences 

1) Use the broken retinal scan panel to open the door, then exit the test chamber.  Make sure you pick up the crowbar you see by one of the doors
on the way to the main lobby.

2) Find your way back to the main lobby security desk, then use your
crowbar to smash open the vent panel by the floor on the right.  Go through the hole into the vent. 

3) There are a few headcrabs near the vent on the other side.   If you brought the guard with you that you met in the hall (by Using him), he'll shoot at least one of them for you.  Also watch out for the exploding computer.

4) Climb up and exit through the other air duct (smash it with your crowbar to open it -- get used to doing this, there are quite a few vents in the game, and many of them must be smashed with the crowbar or shot open with a gun -- crowbar saves ammo, which you'll need).

5) Pick up the gun from the dead guard you'll find.  You could also kill the guard you had following you around (using the crowbar) and take his gun, but it's not necessary (and not very nice).

6) Keep walking to the end of the hall, kill the monster on the other side of the iron bar door (which you can't open).  Then drop down through the square hole into the sewer.  Inside the sewer there are two open holes in the roof (one you just dropped through) and one covered with a grate.  Note the location of the 2nd open hole before proceeding.

7) Find the concrete thing with the wheel valve control on it, use it, then walk/swim to the open grate you located.  You can then swim up to the hole and exit, and you'll be on the other side of the iron bar gate.  If you killed the monster from the other side, this part will be a bit easier. 

8) Use the big lever that's on the platform by the huge lift, then run down and get on the platform before it descends too far.  As you descend, look behind you.  Headcrabs will start falling after you.  Don't try too hard to kill them, just dodge them by moving to the side and opposite their direction of motion as they fly by.

9) Be careful on the steel-grating bridge.  It will break when you step on it. To get around to the opening on the left, jump up onto the silver pipes and walk around.  Once at the other side, you can try to jump for the opening, or break the grate to your right with the crowbar and crawl through -- it takes you to the same place.

10) Watch out for the hanging tongue things while crossing the water.  You can jump into the water, or push boxes in to make a bridge.  Go left and up the ladder, out the door, then in the other door.

11) Continue walking along the corridors until you find the elevator.  Use the button outside to open the door and walk inside, then use the button inside to activate the elevator.

Office Complex 

1) Once outside the elevator break the grate on the wall by the floor near the electrical wire that's shooting sparks.  Stay clear of the wire, and wait a bit first so the headcrabs come for you and get zapped.  Crawl into the vent shaft.

2) Crawl to the right, bust the grate with the crowbar (watch the scientist get eaten by the tongue monster), and then jump down into the room.  Find the electrical room door, go inside and turn off the main power.  The lights will go off, so use your flashlight to navigate around the room (watch for more tongue monsters).   You can then open the door to the hall by the elevator and the electrical wire, which will now be safe to pass.

3) Break the glass in the window at the end of the hall and climb through. Then break through the crates to proceed.

4) Get the shotgun and shells from atop the green box, then kill the alien that attacks the guard behind the fence.  If you don't save him, you can't get behind the gate (he opens it for you if he's alive), and there's some ammo and health inside. There is also ammo and health to be found by busting the crates below the catwalk.

7) Go to the flooded room, climb in and jump on objects to avoid touching the water (and electric shock).  Find the light switch on the left wall and turn it off to make the water safe to touch, then get the goodies from the cabinets before busting the vent on the left wall and climbing out of the room.  Watch out for the fan in the vent shaft (duck). 

8) Move the small and large crates to make two steps up to the ladder in the hall by the locked door.  Break all the vent covers in the shaft, but you might want to save before exiting the last one -- there's a security gun just outside.

9) Either duck and shoot the security gun with the shotgun to destroy it, or jump down and run for the switch under it to turn it off.

10)  Climb up the stairs after getting the guard follow you by using him -- they make for a great distraction target for the security guns you'll run across.  Then go out the EXIT door and up the stairs.  There you'll find another guard to help you if you managed to get the other one killed.

11) Stop by the room to the left and down to pick up a few grenades, the go
back to the right and break open the boarded-up exit with your crowbar. 
Walk through (the flashlight helps) and find the freezer door, open it by using the handle to the left.  But before entering the freezer, get all the health and ammo you can hold from the previous area -- once inside the freezer you can't go back out.  

12) Inside the freezer, walk around to the left and find a red switch.  Use it to start the cart moving back and forth along the rail on the ceiling. 

13) Go back to the entry door and climb up the ladder, then smash open the vent and crawl through the vents and across the shelves until you come out near the track of the ceiling-cart.  

14) When the cart moves by, jump on and cross to the other side.   You may need to smash the crates on the cart with the crowbar to get on, and you may need to wait until the cart comes around again to get off at the vent on the other side.  Getting stuck between the cart and a wall or shelf is fatal.

15) Keep climbing up the vent shaft and exit up to the left.   To the right there is a dead guard and a few HEV power cells that might come in handy. 

16) Go up the stairs and find the open elevator shaft.  Inside, on the far, wall is a ladder to which you can just barely jump (don't jump too early, and consider saving before trying this one -- a fall is fatal).

17) Keep climbing up ladders until you can jump up on top of the elevator. There is no way to save the scientist who is hanging by his fingernails above you -- he'll fall as soon as you hit the elevator.

18) Once atop the elevator, find the access panel and smash it open with
your crowbar and drop inside.  The panel is at the rear left, and the flashlight will help you find it more easily.

We've got Hostiles
(Maps in this chapter:  c1a3.bsp, c1a3a.bsp, c1a3b.bsp, c1a3c.bsp,
c1a3d.bsp) 

1) Watch out for security guns, trip wires (red lasers, which activate sentry guns in the area and close fire doors), and trip mine lasers (blue lasers, which will blow up the trip mine -- and you -- if crossed by anything, including an enemy).  It's pretty painful to take on a sentry gun head on -- it's best to avoid activating them at all by ducking under or jumping over.  If you do activate one, strafe out from behind a wall or crate and take a shot with your shotgun (both barrels preferred, use Alt Fire) and then strafe back to safety before trying again.

2) When trying to creep through the area without activating sentry guards (by avoiding touching the red lasers), watch out for aliens that may appear and kill them quickly -- they can activate the guns as easily as you can.   If you've destroyed all the sentry guns in an area, it's safe to cross the red lasers -- nothing will happen when you do (assuming you destroyed all of the sentry guns).

3) Creep past the lasers and guns (touching a sentry gun sets it off also), climb the crates and jump down to the hallway.  Watch out, there are more guns there.

4) There's a pretty hairy area with sentry guns, a wet slippery floor, and an open elevator shaft (a fatal fall).  You may want to grenade the sentry guns in this area to get past, then the red lasers are harmless.  Be careful grenading near fire doors, as breaking the glass on their wall switches will close the doors.  They can usually be re-opened with the switch on the wall.

5) Make sure you don't cross a blue beam -- those are trip mines, and they blow up when you do.  They inflict heavy damage.  Also be careful not to push a crate or box into one, or move a box that a blue beam is hitting. 

6) Climb up the ladders to the exit. There you'll see a scientist run to the soldiers, thinking he's getting rescued.  While the soldiers mercilessly slaughter the scientist, blast them with grenades.   Note that pressing the fire button with a grenade in-hand pulls the pin, but you don't throw it until you release the button.  Try to time it so that the grenade explodes soon after hitting the target area, of the soldiers will run away before it explodes (they aren't stupid!)

7) Exit by using the freight elevator, then go out the firedoor onto the
catwalk.  At the fork, go right.  Find the conveyor belt and walk up it (the wrong way), in the next room you can climb the crates to get back onto the conveyor belt and continue walking up it the wrong way.

8) Destroy the sentry guns below with a grenade, then jump down.   This is much easier than trying to come through this area by the other way (by not using the conveyor belts).  Keep an eye out for the sentry gun behind the open fire door.

9) Climb the stairs in the warehouse and wait for the soldiers and the aliens to kill a few of each other before taking them on.  The soldiers are tough in this area, and they will try to flank you.  They are also deadly accurate with a grenade toss, so if you see one coming, take cover.

10) Walk up the catwalks to the top of the room and go down the corridor.  Kill all of the soldiers from this height advantaged position before going onto the floor.  Once down, take the elevator up to the surface.  Save here, it's nasty up above.

11) If you kill the soldiers that the plane drops off, they will just keep bringing more.  Your best bet is to make a run for the bunker (to the left, near the middle of the outdoor area) -- running around the perimeter of the area seems a bit safer than the middle. 20) open the door to the ventilation shaft, go down to the bottom.   Once inside the bunker, dive down the ladder as quickly as possible and take cover.

12) In the vent system, drop past the (deadly) fan blades in the far right corner.  Then exit the fan chamber through the middle vent (the others have a few goodies in them, but are dead ends). 

13) Once outside the vent, use the control on the computer panel to open the silo door, and then exit.  

Blast Pit 
(Maps in this chapter: c1a4.bsp, c1a4b.bsp, c1a4d.bsp, c1a4e.bsp,
c1a4f.bsp, c1a4g.bsp, c1a4i.bsp, c1a4j.bsp, c1a4k.bsp) 

1) Use your crowbar to break the barrier and duck under the hazard
barriers.  Then enter the control room to your right and use the switch there.  You can exit by using the freight elevator.

2) Jump up on the train, and press use to activate its controls.   When the big arrow thing appears on your HUD, forward increases speed, and back
decreases it.  Use again or strafe to either side to let go of the controls and leave the train. 

3)  Running train at full speed will help you avoid hits from the monsters in the tunnel (and run over a few in the process).  Once you smash through the barrier, you can't stop the train.  So either stop right after the barrier and climb over the pipes up to the ladder, or prepare to swim to the low box in the center of the slime when you go flying off of the train.

4) Personally, I found flying through the air a lot of fun, and it doesn't cause much damage if you get out of the slime and onto a box pretty quickly. You can then jump to the other boxes and make your way to the platform opposite the slime.   Either way, next you can jump up onto the walkway to get to the ladder which leads you up into the pipe. 

5) Next climb the ladder and get on top of the pipe so you can walk past the slime, and once inside the big slime-filled room, walk along the upper pipes and jump over the rail and onto the platform.  From there you can take the elevator up and out.

6) When exiting the elevator you'll run into an alien.  You can shoot the canisters next to it to cause an explosion that will kill it.  Make sure you're not too close when you do.  It's tricky not to cause the explosion, but if you can manage to avoid it do so, otherwise you'll have to jump across the bridge that gets damaged in the blast.

7) Use the switch by the door to open up the airlock, and step inside. 
Another switch is waiting, which you must use to get through the airlock. Note that the scientist here in the test fire control room cannot be saved -- he's a goner.

8) Before entering the test fire chamber, shoot the crates that block the ladder to your left. It's much easier to do this now than while you're trying to creep past the tentacle.  If you break the boxes while inside the chamber, the tentacle will hear you and attack.

9) Note that the "Test Fire" switch on the panel cannot be activated until you turn on the power, oxygen, and fuel (this is how you destroy the tentacle -- there is no other way).  You'll need to creep past the tentacle at least twice to activate these, and doing so can be tricky.  The easy way is to walk (hold down the 'walk' key if you have auto-run on) or crouch while moving past him, being careful to avoid the whapping tentacles.  The hard way is to distract the tentacle with grenades and/or shotgun blasts, causing it to briefly retreat into the hole while you run by.  Either way is nerve-wracking, take your pick.  go to the second level from the bottom. 

10) First we'll turn on the oxygen and fuel (although the order is unimportant, you could turn on the power first if you want).  Creep around the tentacle and through the door on the second floor of the test chamber.  Run fast after breaking the boards with your crowbar, because the tentacle will hear you and attack as soon as you do.  Walk across the bridge and follow the red and blue pipes down the halls.

11) Enter the sewer grate by ducking on top of it, aiming down, and
smashing it with the the crowbar.  Follow along the pipe and turn left at the fork (right is a dead end), then climb the ladder.

12) Climb down the ladders to get below the huge fan.  Save here, this is tricky.  Turn on the switch and run immediately back up the ladder, trying to avoid the fan blades.  Once above it, wait until the fan spins up to full speed before proceeding.

13) Look up and notice the boards over the roof.  You have a choice for
dealing with them:  the visually appealing way is to toss a grenade
(assuming you have one) out above the blades and watch as it flies up and explodes through the boards.  If you have no grenades, or want to save them, just jump out above the fan blades (trust me :) and take out the boards with the crowbar once you float up to them.

14) Once above the boards, break the vent cover on the wall with the
crowbar and climb through.  Ducking helps here.

15) Crawl along the shaft until you get to the Oxygen/Fuel control room.  Turn on (use) both switches on the control panel.  You'll know they're both on by the lights and the bubbles that will start flowing in the pipes.  Then exit by climbing up the ladder and follow the blue and orange pipes back to the tentacle.

16) Next we'll turn on the power so we can make some tentacle jerky.  
Creep through the test fire chamber again and exit the door on the lower
level. 

17) Jump over the broken section of the metal walkway -- I know it looks too far to jump, but it isn't.  Just make sure you don't jump too soon.   Save before trying.

18) Before crossing the puddle of water round up all the boxes and crates you can find and build a bridge across it.  It's harmless now, but once you turn on the power it will become electrified, and then it's very difficult to cross and survive.  Make sure that you can jump onto and off of your crate bridge without touching even a drop of the water.  Update:  Keith sent in a clever strategy that doesn't require this preparation.  See #24 below for details.

19) Walk over to the catwalk and use the elevator button.  Once on the
elevator, use the button inside to start it up.  The elevator will malfunction and stop half way (or so) up the shaft.  As soon as it does, jump off and grab the ladder on the wall to your left.  If you wait too long, the elevator will fall with you in it and you'll take damage from the radioactive sludge at the bottom before you can climb back up the ladder on the wall.

Larry says you don't need to jump off right away, just wait until it 
starts falling again and when it's close to the platform jump off. No 
damage! (Sounds risky to me).

20) Once at the bottom, climb around on the pipes to avoid touching the
radioactive sludge.

21) Climb the stairs to get to the power generator control area. There are two switches -- one on either side of the generator in the center.  Both have to be turned on to start up the generator, but make sure you are not on top of it when the second switch is activated, or you'll get fried.  

22) Moving around the generator can be tricky.  Avoid getting hit by the
fast-moving platform thing.  It'll kill you.  Just stand for a few moments and watch it run, you'll get the pattern and the timing so that you can safely move around. 

23) Once the the power is on (you'll know if it is), leave the way you came in.  There's a conveniently located ledge you can use to avoid damage from
jumping off of the ladder.

24) Use your crate bridge to avoid touching the (now electrified) water on
the way out.  If you forgot to do so, use one of Keith's strategies:

You can get up on the large stationary box at the end of the hall
(in order to get up on the pipes and walk around the wall on the
pipes OVER the water) if you slide the other boxes up to it then
do the Half-Life spasm jump. Run then hit the JUMP and
CROUCH keys simultaneously. I'm told this will get you up there.
You will NEED this spasm jump later on in the game. (BTW, you
don't need the Jump Pack thing for this jump.)

This is my solution that I found: I slid two boxes end to end into
the water on the left side by the wall. Then I lined up two more
boxes right next to those in the water. Then I stood on the left pair
of boxes facing the second row of boxes. This is the weird part --
I held down the USE key and strafed left. This sent the second
row of boxes sliding out into the water. With the correct slide I
was able to jump from box to box and get over the water without
damage!!

25) Go back to the top and into the test fire control room by the tentacle.  All the lights on the panel should be lit (if not, you didn't turn on power, fuel, and oxygen).  Press fire and watch the action.  You'll probably take a little heat damage in the process since the doors will close and lock while the test fire is underway, but it's not fatal (and worth it :) 

26) Enter the test fire chamber and leave the room through the hole in the
floor in which the tentacle was sitting (save first, drowning is common here).   Make sure you fall in the center of the hole, or you'll hit the side on the way down and die.  There's a nice .357 magnum waiting for you at the bottom of the water if you make it, so get it.

27) There are two fans at the bottom of the pool also; ignore them, they can't be broken open or used to escape.  Note that the pool looks as if it is surrounded by four equally spaced pipes, two on each side, but one is
missing.  That missing pipe is your way out.  Swim up to that side and up out of the pool.

28) Continue walking on the pipes and go to the end.  When you see the
wheel. jump off of that pipe into the one by the wall that has a broken grate in it.  Climb inside and keep walking, but be careful.  You'll notice a slight change in color of the pipe in one area, and that part is going to break off when you step on it.   Jump back immediately when the breaking starts and you can avoid going down with it, which causes a lot of damage.

29) Once the pipe breaks, assuming you didn't go down with it, walk to the
left and drop down between the pipe and the steel beam.  You'll land on the
ceiling of the room below, and then can jump the rest of the way down.  Don't worry too much about taking a few hits of damage; there are health kits at the bottom. 

Power Up 
(Maps in this chapter: c2a1.bsp, c2a1a.bsp, c2a1b.bsp) 

1) Don't hesitate at the start, try to make it across the open area and to the tunnel to the left while the big ugly beast is fighting with the marines.   They should all ignore you while they're trying to kill one another.  It'll be harder to make it by without damage once the monster smacks the marines.

2) Continue down the tunnels until you come upon red doors and a wheel. 
Use the wheel to open the doors (hold use down until they open enough to
go through) and ten climb up the tunnel to the top.

3) Go across the open area and up to the other side, then go left towards the power generator (follow the signs).  Once you get to the elevator, send it down (without you on it) by using the button.  Then you can shoot the trip mines below, or better yet send down a detpack on the elevator and set it off from the safety of above.  Bring the elevator back up (use the button), climb aboard and go down with it this time.

4) Take the stairs down and continue all the way to the bottom.   Watch out
for the freaky leech-worms in the water -- they don't do much damage,
especially if you have some HEV suit power remaining, but they gross me
out bigtime (the crowbar works on them nicely).  Once you make it to the
(non-operational) power generator, use your crowbar to smash the boxes
that are blocking the pistons (on the front of the generator).

5) Climb back up the stairs and go to the fan control panels.   One fan is not on, so you have to turn it on with the switch there.  Now the power generator is on, so you can head back up to the elevator and then to where that lovely monster is waiting for you.  Note that the track main power still has to be activated for you to use the train in the center of the open area (by the monster).

6) Find the the boarded up doorway labeled  "Track Control".  Ignore the
switch for now, just jump out the window and let the monster follow you.  Go down the large tunnel on the left (the one that isn't obviously a dead end) all the way to the far wall of the room at the end.  Pull the switch there and when the monster walks between the two huge electrodes, he'll fry like an egg.

7) Exit the room through the door, which will lead back around to the tunnel you took to get there.  Go back to the large open area with the train car and jump on -- you now have power.  Drive the train straight (full speed is fine) until it stops at the rotating platform on the track.  Go back into the track control room and use the switch there.  The rotating platform will spin, pointing the train car in the direction you want to go, then hop out the window, back onto the train car, and smash through the barrier at full speed.

On A Rail

1) Once your train car stops at the guard, listen to his story and get off the car to use the switch on the wall.  The gate will raise, and you can continue driving the2 train along.  Avoid the water and the center track of the rails -- they will damage you (to the tune of about 10 points per touch).

2) Continue driving the train straight ahead until you see the second track switch sign.  Shoot the sign to change the way the arrow points (you want to go straight instead of turning), and your train car will switch tracks at that point.

3) Stop your train car at the platform by the stairs and the monster.  Take out the monster and climb the stairs, but don't smash the crates -- there's a sentry gun behind them.  Instead, toss a grenade to the other side of the crates and take out the gun with no hassle.  Then enter the little room and use the switch to move the hanging hook that was blocking the train tracks.

4) At the next track switch sign, shoot it to change tracks.   That should take you down the track where the hanging hook was blocking before you moved it.  Once you make it to the next gate, get off the train and use the switch to raise it, then continue riding the train down the track.

5) When the train car stops at the end, you have to get off and go it on foot. Shoot the marines on the left and keep moving.  Smash open the
boarded-up room to find the friendly guard and get him to join you (use him).

6) Be careful turning the next corner -- there is a feisty mounted artillery gun in a bunker straight ahead that will perforate you if you stand there long. It can also shoot and destroy crates, so once it knows you're there, run like crazy up to the right side of it's bunker.  There's just enough space there between the wall and the bunker to toss in a grenade or two and take out the gun.

7) If you're hurting at this point, climb up atop the blast doors and get the health and HEV power cells before entering the blast doors.  Once inside, shoot or toss a grenade at the trip mines and stand clear.

8) Walk down the stairs to find another train car and take it for a spin.  Watch out for falling debris (that can knock you off your train and onto the electrified rail as your car runs off without you) and red sentry gun lasers.  Duck under them to avoid unnecessary firefights with sentry guns. 

9) Also watch out for the marine with the rocket launcher around one of the bends in the track.  It's best to disembark to take him on, as he aims for the train car pretty darn well.  Continue along the track.  If you lost your train when fighting the rocket launcher, you'll find it up ahead soon (it stops at the next gate).

10) On the platform by the train track kill a few aliens and then hop up over the green boxes blocking the doorway. You have to duck at the peak of your jump to do this (see the Hazard Course for details if you haven't already).   Once inside, use the switch to raise the gate on the track and continue down the track on the train car.

11) Continue to the next gate, and then kill everything in the room. To kill the mounted gun, toss a grenade into the bunker with it.  The switch for the next gate is near that bunker.  Feel free to take off on foot at any time -- the train is not critical to completion, but it does save a little walking time.  The train car also comes in handy for clearing out trip mines -- you can just let it go on it's own and catch up with it later (it will stop at gates).

12) The train car also makes a pretty good shield against incoming rockets, which you will run into at least a few times in the tunnels.  Duck behind the control panel and speed by to avoid them, there is no benefit in taking the time to destroy them.

13) At the next track switch sign, shoot it so that you continue going
straight. At the next gate, get off and take the ladder down, but be careful not to cross the red sentry gun laser -- near the bottom of the ladder jump away from the wall and strafe to the side at the same time to avoid it.

14) Enter the control room and choose your path.  You can either take out the sentry guns with grenades (why?) or just hop out the window and avoid all of the red lasers while walking away to safety.  You're going to need your ammo soon anyway :) 

15) At the end of this tunnel is a rather ugly situation: a mounted gun in a bunker right in the tunnel, a mounted machine gun behind some sand bags just to the right of it, and a load of marines crawling around the large room to the right of that.  First kill the machine gunner, then push the crates as cover while walking up by the bunker.  Climb up the bunker and throw in a grenade to shut it down.   You're on your own with the firefight with the marines in the main room.

16) Once you enter the blast doors, watch out for red sentry gun lasers. 
There are several of them up a staircase, and these are attached to a few hundred points of explosives lining the room.  One wrong move and it's all over.   To get past the lasers, first push the larger box under the last beam.  Then crawl under the first two lasers and jump from the stairs on to the box.  You can jump over the last red laser from the box.

17)  Take out the few guards (a nice silent snipe with the alternate fire crossbow works wonders) and go press the launch button in the control room overlooking the launch pit.  Enjoy the show.

18) Leave the building (careful of the red lasers -- they're still there) and then exit out the blast doors (the way you came in to the launch area).

19) The large doors to your left will now be open (watch out for the sniper off to the right and up on the rocks), go through the newly opened doors. 

Apprehension 
(Maps in this chapter: c2a3.bsp, c2a3a.bsp, c2a3b.bsp, c2a3c.bsp,
c2a3d.bsp, c2a3e.bsp) 

1) There's no way to stop the train; get off or ride it all the way in.  At the bottom of the water is a set of barrels or canisters tied down.  If you swim down and "use" the lock on them, they will float up to the surface and make a bridge over which you can walk to get up the other side. 

2) Walk around the catwalks and jump into the water.    Swim around until you find the sloped floor that leads to the exit of the water.  Through you'll probably take damage from not having enough oxygen, it's only temporary and your health will return shortly.

3) In the room with the cage hanging from the ceiling, go around the
catwalks to get to the top.  Climb out onto the cage support and enter the cage. In a few seconds the cage will drop into the water -- you can stay put and fire from there or, easier, move up and out and near a wall to prevent attacks from behind.   Shoot the big fish with the crossbow and/or the 9mm pistol (it also fires underwater).

4) Swim down and open the grate by holding "use" down on the red wheel. 
It starts closing as soon as you stop holding "use," so be sure to open it enough to allow yourself to swim through.

5) Climb the stairs and walk along the catwalks.  They will break apart in places, so stay near the center where the main support is (it stays while the rest breaks).  If you fall off, you have to go back to get back up there.

6) When you come to the steel cage wall, you can try to jump past the
hanging electrical wire, but it will probably hit you for a few points.  Instead, jump in the water and swim through the opening to your right.

7)  Climb the stairs and chose one of two methods to get to the catwalk on the opposite side of the room: 1)  Push the two crates down to the floor and build a staircase up to the broken ladder (smash the boxes blocking it) or 2) Use the button on the control panel to start the pistons moving and jump across them to the other side.

8) Once you kill everything in the next room,  the scientist will open the door for you.  Like he says, there is nothing all that interesting in the cold room, so just run as fast as possible to the ladder that leads down.  (Turn right, then left, then right again).

9) This will be your first meeting with the sniper babes, and they are tough.  Explosives work if you can figure out where they are or coax them to chase you.  Sniping with the crossbow works well if you can find their hiding places (two are on the ground floor, and one is up on the catwalk).  A full-on frontal assault with both barrels of a shotgun (my solution) works well if you're quick, a good aim, and a relentless pursuer.  Save before trying.

10) After killing all three of the sniper babes (I can't imagine that you'd get very far just trying to sneak past, but it's worth a shot if that's your style), go up the ramp to get to the surface access control.  Hold down 'use' at the wheel to open the large doors below.  Save before entering (see below for why).

11) Although I've heard stories of people doing so (lies?), I was totally unable to avoid being caught and knocked out when entering the dark room. If you want to try, I suggest loading up the room with detpacks and blowing them up before entering.  Didn't work for me.  Besides, apprehension isn't that bad...(except for losing all your weapons).  I've also heard of a few people for whom the game seems to just stop at this point -- they get stuck (can't move) in a dark room with a walkway barely visible.  reloading a saved game just before being caught worked fine -- it should only take a few
seconds before the dragging scene begins.

12) After the dragging scene (cool), you'll wake up in a trash compactor that is slowly closing in.  Take your time and climb up the boxes and crates to avoid assuming the role of a pancake.  Once up and out, you can walk across the closed walls of the compactor to get your crowbar, and then leave the room via the grate on the floor on the left side of the compactor (smash it with your crowbar).

Residue Processing 
(Maps in this chapter: c2a4.bsp, c2a4a.bsp, c2a4b.bsp, c2a4c.bsp,
c2a4d.bsp, c2a4e.bsp, c2a4f.bsp, c2a4g.bsp) 

1) The flow control wheel will raise or lower an elevator-like platform inside the cylindrical tower.  Use this to leave the area.

2) Jump down onto the edge of the vat and leave by walking across the pipe on the other side.  Keep walking on pipes to get to the next vat.

3)  Walking around the edges of the vats is possible, but tricky (they're slippery!) Instead, jump to the plunger thing to your left when it is on the downswing.  Then you can jump from plunger to plunger along the left wall to get out the other side.  If you fall, there's a ladder to get you back to square one to restart.

4) Keep walking and duck under the grinding wheels and cogs.   When you
get to the room of conveyor belts, walk around to the right to the three
switches.  Set all three switches "up" (forward), which should make all
conveyor belts moving away from where you started in this room.

5) Walk back to the control room and press the green button, which will stop all the smooshers, but only for long enough for you to get by -- don't sit around and wait -- run fast.

6) Continue riding forward along the conveyor belts, timing your motion to move past the smooshers (note that they are not all the same -- the first does all long strokes, the second is a long stroke followed by a short one, and the third is a long stroke followed by two short strokes).

7) Drop down from conveyor belt to conveyor belt to find the two belts
running side-by-side.  The one on the right is no good, but the one on the left is laced with two trip mines.  You can shoot the first one, but not the second, since it is around a corner (if you can shoot it, you're close enough to be killed by the blast).  Try this to get by:  exit the conveyor onto the platform to the left (before it enters the wall where the trip mines are).  Drop a detpack onto the conveyor and start counting one-one-thousand, two-one-thousand, ... at six, detonate the detpack and you should take them both out. 

Questionable Ethics 

1) To open the electric door, shoot the electrode on the fence. 

2) The big thing behind the glass will get out if you taunt him, get near the glass, or break the control switch cover.  You have to break the control switch cover to exit.  You can run away from him, or lob a few grenades from your machine gun (alt fire) in his face.

3) In the two jail cells filled with headcrabs there is a hornet gun and a crossbow. To get them without wasting all your ammo on headcrabs, or
risking an all-crossbow assault, open the doors and draw the crabs out. 
Then run into the control room and use the button there -- it will zap
everything in the room.  It may take you a few zaps to get them all.

4)  Watch out for trip mines in this building, there are many.   Also try to let the marines fight the monsters as much as possible -- if you lay low for a bit in each areas they will do a lot of your work for you, and it's fun to watch.

5) Turn on all four lasers in each of the four rooms at the end of the hallways.  Find the room with the sign that reads "Do Not Obstruct Laser Shield".  Obstruct the laser shield.  Move the crate on the floor so that it blocks the shield that lowers when you activate the mega-laser. 

6) Exit the room through the hole the laser blows in the wall, and jump down the pipes to avoid taking falling damage on the way down.

7) You have enough scientists for a little trial-and-error here, but you should check the patch to the main exit and clear it of hostiles (and sentry guns) before taking one up to open the door for you.   Watch out for sentry guns on the roof on your way out.

Surface Tension 

1) Don't worry about the helicopter, the marines, or the rocket launcher.  Just run and dive into the water to the left of the dam.  If you insist, all of them can be destroyed (including the chopper), but at a cost of much ammo.

2) Kill or evade the big fish in the water, then climb the tower and go inside it and use the switch to make it safe to swim through the gates under the dam.

3) Swim down to the bottom by the dam and find the red wheel.   Hold down use to open the gates of the dam.  Swim through one of them, but be careful when coming up for air on the other side -- do so quickly, the chopper is still looking for you. 

4) Climb the ladder and walk through the pipes, exit and climb up the ladder on the wall of the building.

5) Ignore the tentacle monster in the next area -- you don't have to mess with him at all unless you want some of his goodies.  The other crack in the rocks leads to where you need to go.

6) Walk around the mine field on the left hand perimeter, staying on rocks as much as possible.  Once at the red wheel, turn it to open the storm drain and climb down the ladder (don't fall, it's too far).

7) Walk down the pipe until you see blue sky, then pull out the crossbow and
snipe (alt fire) the marines in the area.  They are above and below you.   Use both barrels of your shotgun on the sentry gun.

8) Climb down the breaking bridge by walking on the wires, or slide down
the large section carefully.  There's a chopper in the area that's pretty easy to avoid, but you can destroy it with two shots from the laser-guided rocket launcher if you want to see the pretty explosion.

9) Once inside the pipes, take a left at the tee creep up the ladder (walk,
don't run) and throw a grenade at the marine's back.  Retreat into the pipe
and exit the other way (right at the tee from before) and jump into the water.  The marines will be looking near where you tossed your 1st grenade, so you can surprise them again from this side.  

10) It takes several rockets to destroy the tank so just try and run around it and do it with two detpacks (or grenades) instead.  Open the gate and
replenish supplies. 

11) The next tank (?) is tough to kill, it's better to try and strafe back and forth to avoid his shots.

12) Stay to the left in the next minefield, or shoot the ground several feet in front of you to take out any mines in the area.  Also watch out for the snipers up in the windows.  A grenade from your launcher (machine gun alt fire) it the easiest way to take out snipers.  There are two snipers in this map.

13)  Shoot the exploding barrels to turn off the power before trying to climb up the fallen electrical tower to the roof.  Watch out for the sniper behind you when crawling under the barbed wire to get to it.

14) Walk around the roof (first left) to find the hole in it, and drop in onto the larger crate there to avoid falling damage.

15) Leave the chicken scientists and be very careful around the trip mines -- they are everywhere.  Push a crate up to the one on the stairs to jump over, or just jump on the railing to avoid it.

16) Jump and duck trip mines to make your way to the main room (that's just loaded with trip mines) and find the elevator platform by the wall (not the one in the center of the room -- yet).  Break the box on the elevator platform by the wall so that when you raise the lift it won't activate the trip min above it.  Be careful not to break or move the crate next to it that has a trip laser already hitting it on the other side.

17)  Jump and duck your way into the control room and use the switch to
raise the platform.  Jump out onto this platform, then jump over the laser trip mines and onto the elevator platform in the middle of the floor.  Use the button there to lower the elevator, taking you to safety and leaving the scientist screwed and cowering in that room :)

18) As the aliens drop in, the air raids will come and kill them.  No sweat, but stay clear and don't be near the surface when the bombs drop.  Then run past the tank, strafing to dodge it's fire.

19) Turn right around the corner, but watch out for the sniper as you climb the stairs.  Find the guard and get him to open the storage room for you (use him, and lead him to the door).

20) Jump out the window and walk along the ledge to the ladder that leads to the roof of the other building (across the alley).  Kill everyone in the bombed building and then jump across the twisted girders and debris to exit on the other side. 

21) Climb up to the big gun and use it to blast open the big doors.   You can also use it to dispatch any marines that might be following you.  Exit through the big doors.

22)  Be careful exiting the next door, there are tons of those big
hornet-gun-toting baddies out there, usually three at a time, but they won't spawn until you step in certain areas.  Kill the first three and make a run for it.  

23) Use the conveniently located mounted machine gun to take out the
hordes of lightning monsters coming down the sloped tunnel.  Just duck
down behind it, use the gun, and hold down fire while spraying hot lead all over the place -- they keep coming in several waves to just peek up to check on them until you're sure they're all gone.

24) Use the bouncy-crater (step on it) to get atop the roof, then watch the marines fight the aliens.  Clean up the survivors.  Drop down and smash open the vent with your crowbar.  Be careful!  The vent shaft is crawling with snarks, and they are a pain.  Some sort of explosives are handy for removing the bulk of them, but you'll probably have to run from a few.  They are hard to shoot, and they hit pretty hard for their size.  Their weakness is their short life-span.  If you can evade them for about 20 seconds of so, they explode.  I wasted a lot of ammo on those little chum toads (what they were called before the game was released) before I realized this.

25) Once inside the tunnel, find the vent cover and smash it open.   Soon after, the marines below will hear you and start perforating the vent with bullet holes (this effect is great) -- back up and fill the room with snarks, it's a blast to watch.  You have to get very close to the hole in the floor of the vent shaft to drop them, but even if you take a few hits it's worth it.

26) After killing the marines, exit by the door on the right.   If you wait too long, someone will throw a grenade in from outside and seal off the door with debris.  If this happens, use the switch hanging from the ceiling by the car lift and hop on, it will raise up and you can jump out through the hole in the wall. 

27) Once outside, use the big mounted gun to blast through the big doors to exit the area. 

28) Jump over the broken catwalk -- it's far, but possible without a super long jump.  Don't jump too soon.  You may find it easier to jump up on the railing first, and then jump across. 

29) Use the bouncy crater to get to the roof then open up the pipe and climb through.  Find the guard at the end and get him to follow you, you'll need him to open the door at the bottom, and the door after that (so don't kill him!)

30) At the next big flame-throwing monster, run away and don't look back -- he'll get it bad in a minute.  Bounce on the crater over the wall and into the pool.  Then climb quickly across the pipe and onto the platform with the green map and  he radio.  One of the controls moves the horizontal aiming, one moves the vertical, and one calls in the air strike.  Examine the map (it's a map of the large area you are in now) and figure out where the large door you entered the area is on the map (lower left).

31)  Line up the intersection of the two lines on the map with the area just outside of the door by which you entered this area.  Turn around and wait for the flame-throwing monster -- he'll be there soon.  As soon as you see him, use the button to call in the air strike and he's toast.  Best boss kill ever in a fps, bar none.

32) Next take your time and call in air strikes to destroy three targets:  (1) the right wall of the fortress-like area across the moat (2) the door inside the fortress walls, and (3) the large tower in front of you.  Then simply walk across the tower (which falls conveniently to let you cross the moat) and through the door in the now breached fortress area.

Forget About Freeman 

1) Get ready for some falling ceiling action.  Go to your right and  wait for the third segment to fall from the roof (it's shorter than the others) and jump on top of it.  Wait there until the rest of the roof falls and make your way to the exit on the left.

2) Walk to the tee and go right, then use the wheel to open the hatch cover. Avoid the red sentry gun lasers (or destroy the sentry guns).

3) Go down either of the "West" tunnels and jump over the grate to exit the area.  Avoid or destroy the tank, then ride the elevator down.

4) Turn right at the tee, then use the tank to blow a hole through the door.  Be ready for a slew of monsters to come through when you do.  The
combination of lightning-shooters and hornet-shooters is especially
annoying.  Trip mines and your own hornet gun work well.

5) Be careful walking through the big door -- there's a laser gun to the left and several hornet-shooting monsters on wither side.  Strafe out from cover just long enough to fire a rocket at the laser gun, then strafe back to cover (turn off your laser guidance system with alt fire or you'll miss when you strafe for cover).   Use your hornet-gun to kill the hornet-shooting monsters -- you can shoot them from the safety of behind the wall.

Lambda Core 

1) Use the switch in the control room and ride the elevator down, then watch out for the sniper babes.  

4) Only after you kill everyone in the area will the scientist open the door for you.  Walk to the right and get the big gun, then go back to the elevator that leads to the coolant system.

5) Go to each of the pump rooms and use the switches there to activate both pumps. Then go to the auxiliary reactor and jump down into the water. Crawl through the maintenance tunnel and use each of the two switches on either side of the core.  Watch for and avoid the sparks on your way out (climb up the ladders to the top and leave).

6) Climb up the elevator shaft and jump off the ladder to get to the upper level.  Here there are steam valves you can open (use) to kill the monsters in the area.  It's fun to watch.  The teleporter here is just to show you how they work -- green ones are entrances and orange ones are exits.  

7) Find the door with the sign that says "Core Level B" , go inside and start the teleporting festival.  This is perhaps the only really annoying puzzle in the entire game, but it's not too bad once you figure it out (duh).   You have to jump into each teleporter on the tower, in numeric order (lowest one on each level), and time your jump so that then you appear at the orange teleport exit at the next level up, you will land on a rotating platform and not fall to the bottom.  I suggest saving after each successful teleport.

Neal also points out the following tips:  As you jump onto each rotating
platform, walk to the leading edge (in the direction you are moving). That way, when you  jump into a teleport (don't delay), you will be aligned correctly to land onto the next higher platform. 

8) Once you get to the top platform (a new area) don't jump back into the teleporter!  Look behind you for a door, open it and go inside.   Climb the ladder and wait for the scientist to open the door.

9) Once inside, stock up on weapons (health and HEV power are in the next room, so don't worry).  Make sure you take the jump pack with you (right by the door) or the next part is much harder.  Save before proceeding in any case.

10)  Kill the flying monsters to keep both you and the scientist alive until he tells you it's ok to jump into the teleporter.  When he says go, do it -- you don't have long.

Xen 

1) If you didn't take the Hazard Course, now is the time when you'll wish you had (so save and go do it!).  Use the super long jump to jump from platform to platform, making your way to the large center area.  Save often. 

2) On the center planet thing there is a little pool of water that will restore your health while you stand in it (these are all over Xen, so look for them). Near this pool is the entrance to the center of the planet thing you're on.

3) Walk to each of the three mushroom things and use them, they will open up as you do each one.   Break open all of the web stuff with your crowbar and release the yellow butterfly things that will float into each of the mushrooms and activate a teleporter in the center.  Go into the teleporter.  

Gonarch's Lair 

1) Shoot the spider repeatedly in the belly-sac thing hanging underneath it. eep doing this until the spider runs away, then follow it, and shoot its sac some more.

2)  There's a webbed area in the center in the second area that you can
jump into (if you're careful and don't miss the ledges beneath it).  You'll find a health pool (and some headcrabs) down there.  Use the bouncy crater to get back up for more sac-shooting fun.  

3) Keep shooting sac and chasing spider until you drop down below a web
on the third area.  Unleash all your ammo on his sac while you're underneath it -- soon it'll drop down with you.  Kill the spider (remember, only sac-hits do damage), and then hide behind the whapping trees to let them finish off the headcrabs and baby headcrabs.

Comment:  Psyci suggests not dropping down below on the third area. 
Rather, let the spider drop, then dump every snark you have into the pit
with it.  Seems they know to go for the sac too :)

Interloper 

1) Look for healing pools in the caves if the spider got a piece of you -- you'll need decent health to finish this level. Watch out for the pits that open and close -- you'll die if you fall inside one.

2) Find the small yellow area in the cave to the left and go inside.   Use your crowbar to smash the webbing around the base of the white column. Climb on the tower and ride it up to the top.

3) Like you did at the beginning of Xen, jump from rock to rock to make your way to the low area near the teleporter.  Watch out for the lightning-shooting aliens (duck).  Finally, jump on the back of one of the bird things and ride into the teleporter. 

4) Walk (don't run) past the tentacle or climb over the rocks (watch out for another flame-throwing monster) to get to yet another teleporter.

5) Once inside the place where the lightning-shooting aliens are slaving
away at some space-beer-brewing factory, take the elevator things up to the conveyor belts.  Don't shoot the slaves in this area -- they'll leave you alone unless you attack.

6) One of the conveyor belts enters a hole that does not have a blue
force-field on it.  Enter this hole.  Keep going up and right until your way is blocked by big beer kegs.  These kegs each contain an ugly monster that
hates you, so avoid breaking them like the plague.

7)  If you back up and super long jump, you can clear the kegs blocking the path (it's low gravity -- try it).  If you can't get that to work, drop a detpack by the kegs but don't detonate it.  Switch to the shotgun and blast open the keg, then switch back to the detpack and detonate the monster than comes out.

8) Look for a red vent-shaft type thing with weird globs of light inside.  Go in there (seriously).  Keep going until you enter a huge, tall room. Whip out the crossbow and snipe everything in sight with alt fire.  Keep working your way upward and sniping the aliens.  You'll have to ride up a few odd spinning cog platforms and kill loads of flying things, but it's not too bad.  At the top is an (obvious) teleporter; jump inside.

Nihilanth 

1) Shoot the triangles until each explodes and avoid the green teleporter
balls by ducking behind rocks -- getting teleported into those other rooms really sucks.

2) Shoot the big baby until his heads opens up on the top (the head just
opens up on the top a little, you may miss this lovely event if you're not bouncing up high) on the bouncy craters on the floor. 

3) Bounce up high over and over until you can get a good shot at his brain
inside the opening in his head (one or two detpacks dropped in his gaping cranium should do the trick). 

Neal says: Here's how I killed the final boss: Using the bouncer on the floor I got to the upper ledge bouncer.  From there I jumped onto his head.  He can't attack you while you're standing there! I then smashed his brain with the crowbar.  That's right! I killed him with the "weakest" weapon of the game.  

4) Save the game here, because there are two endings, slightly different
depending on your decision (you'll see), and you'll probably want to see both without fighting the big baby again.

--------Versions---------

.9 - guide started

1.0 - Updated

1.1 - Finished brief guide

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